NOTES ON IDENTIFICATION OF TROPICAL WOOD 



49 



wide horizontally as the borders of the 

 pits themselves. The pits are uniformly 

 arranged over the entire surface of the 

 vessels. They are close together, uni- 

 form in size,, and hexagonal in outline. 

 The partitions between the pit cavities 

 are thin and delicate, resembling the 

 walls of honeycombs. The regularity 

 in the number and occurrence of pits 

 in vessel walls is rarely disturbed, but 

 there are places where the pits are not 

 fully developed ; here the pit canals are 

 present and the cavities are wanting. 

 The lenticular pit cavities and the slit- 

 like pit canals can best be seen in trans- 

 verse sections, especially if the section 

 be treated with a solution of iodine and 

 sulphuric acid or chloriodide of zinc. 

 The pit canals in the cross-w r alls of 

 abutting vessel segments cannot always 

 be clearly distinguished in longitudi- 

 nal sections. The canals themselves 

 are often mistaken for partition walls 

 between the adjoining pits. This error 

 may be avoided if one remembers that 

 pit canals always begin where the pit 

 cavities end. The lenticular pit cavities 

 are seen best in longitudinal sections. 

 \Yhere the vessels are adjacent to w^ood 

 parenchyma, the pits within the walls 

 of the latter are the same as those in 

 pith ray cells, and those within the ves- 

 sel walls are bordered. The pits in the 

 cells of wood-parenchyma fibers and 

 pith rays are simple, and in vessels 

 they are bordered, resembling those in 

 tracheids of conifers. The pit cavi- 

 ties, however, are not shown so plainly 

 as they generally are in coniferous 

 woods. 



The cross walls of vessel segments 

 are now always in close union. The 

 portion between the abutting segments 

 is composed of a soluble substance. P>y 

 treating thin sections with potassium 

 chlorate and nitric acid, this substance 

 is dissolved, leaving the cross walls dis- 

 tinctly visible. The vessels are devel- 

 oped directly from wood parenchyma, 

 as may be determined from the inter- 



mediate forms which are very abund 

 ant. especially where more than thre 

 vessels are located side by side. Tw< 

 of these vessels are, then, as a rule, o 

 the usual diameter, and the others ar 

 smaller. 



The structural characters of thi 

 wi H >d are like those of woods related t 

 Robinia, Glcditschia, Hcematoxylo 

 campechianum L., C&salpinia ecliinat 

 Lam., etc.. which are known as legum: 

 nous woods. As was said, the occur 

 rence of vessels as vessel cells and nc 

 as vessel tubes is characteristic of th 

 woods of this group. 



In conclusion, the question to b 

 solved is whether the regular alternat 

 ing bands of wood fibers and woo 

 parenchyma correspond to annual in 

 crement layers. The gross character 

 showing that they do not coincide w r it 

 so-called annual rings have alread 

 been given above. An anatomical in 

 vestigation reveals the fact that ther 

 are no elements present, either in th 

 parenchyma or prosenchyma layei 

 which resemble intermediate forms in 

 variably found in that part of the con 

 centric zone where it changes graduall 

 from early to late wood. Nor is there 

 known wood in which the early growt 

 is composed of tissue wholly differer 

 from that formed later. 



The facts determined thus far sho\ 

 beyond doubt that it is a leguminou 

 wood. There is no analytical key base 

 on structural characters by means o 

 which it can be traced down to it 

 proper genus. Both the gross an 

 minute characters have been carefull 

 compared with those of authentic sam 

 pies of Bowdichia :'ir^'i!oiclcs, wit 

 which they agree in every particulai 

 The generally accepted trade name fo 

 this wood is Sebipira. which is also 

 generic name given to it by Doctor vo 

 Martins in 1828. It had been previ 

 ou sly described, however, by Hum 

 boldt, r>onp1and. and Kunth as 

 dic/iia i-irgihidcs. 



